Appropriate regulation of the level and pattern of breathing is particularly critical in patients with chronic airway disease in whom ventilatory mechanics and gas exchange are disordered. Breathing is regulated by automatic reflex mechanisms mediated by chemoreceptor and mechanoreceptors in the lungs and chest wall. Additionally, breathing appears to be modulated by conscious behavioral influences. These appear to be important in assuring that homeostasis is maintained while minimizing the forces required of the respiratory muscles and reducing the sensations of breathing discomfort. The purpose of the proposed research is to characterize and compare in normal people and patients with chronic airway disease, the behavioral influences controlling breathing and the interplay of behavioral and neurosensory mechanisms regulating the level and pattern of breathing. In these studies psychophysical techniques will be used to evaluate the role of chest wall afferents and chemoreceptor inputs in shaping respiratory sensation. The transmission of sensory information from the ventilatory apparatus to higher brain centers will be studied by examining respiratory related cortical evoked responses. The proposed research will also evaluate the effects of persistent changes in ventilatory system impedance and the consequences of prolonged hypoxemia on respiratory sensation and the central processing of afferent respiratory related neural information. Finally, we will examine the relationships between respiratory sensation, respiratory-related cortical evoked responses and the level and pattern of breathing at rest, during exercise and with added ventilatory loads. The results of these studies will improve our understanding of the altered breathing patterns regularly adopted by patients with chronic airway disease and may form the basis for interventions to minimize dyspnea and prevent respiratory failure.